Many sports leagues, such as the Federation Internationale de Football Association (FIFA), the National Basketball Association (NBA), the National Football League (NFL), Major League Baseball (MLB) and the National Hockey League (NHL), rely on one or more officials, such as referees or umpires, to enforce the rules of the particular sport. Officials usually rely on their own perceptions of game events to make calls enforcing the rules of the game, and as such, are prone to human error. For various reasons, officiating persons may not see all of the activity occurring in the course of play and consequently may fail to notice a violation of the rules, or may even make an erroneous call. In some sports leagues, officials are able to consult replays of broadcast video footage to assist them in making close calls. However, due to the limited view and angle of broadcast cameras, some plays may still be obscured from the camera's view. Furthermore, a human is still required to interact and view the event in question, subjecting the call to the possibility of human error.